78409 has 4 divisors (see below), whose sum is σ = 79380. Its totient is φ = 77440.

The previous prime is 78401. The next prime is 78427. The reversal of 78409 is 90487.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90487 = 41 ⋅2207.

It can be written as a sum of positive squares in 2 ways, for example, as 14400 + 64009 = 120^2 + 253^2 .

It is a cyclic number.

It is not a de Polignac number, because 78409 - 2³ = 78401 is a prime.

It is a super-2 number, since 2×78409² = 12295942562, which contains 22 as substring.

It is a Duffinian number.

78409 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (78401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 352 + ... + 529.

It is an arithmetic number, because the mean of its divisors is an integer number (19845).

2⁷⁸⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

78409 is a deficient number, since it is larger than the sum of its proper divisors (971).

78409 is an equidigital number, since it uses as much as digits as its factorization.

78409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 970.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 78409 is about 280.0160709674. The cubic root of 78409 is about 42.8011368959.

The spelling of 78409 in words is "seventy-eight thousand, four hundred nine".